The invention described herein relates generally to semiconductor metrology and inspection. More specifically, it relates to metrology or inspection that employ scanning of a target with an incident beam.
Generally, the industry of semiconductor manufacturing involves highly complex techniques for fabricating integrated circuits using semiconductor materials which are layered and patterned onto a substrate, such as silicon. Due to the large scale of circuit integration and the decreasing size of semiconductor devices, the device must comply with rigorous specification requirements prior to shipment of the device to the end users or customers.
Typically, particular parameters are measured or characterized within special test structures or targets using a metrology or inspection tool. By way of example, multiple targets are designed to measure misalignment or overlay errors between two adjacent layers. In an inspection or metrology process, an incident beam is usually directed towards a particular spot, which includes a first target. After the incident beam reacts with the first target, the output beam is then collected from the first target. The incident beam is required to remain at the first target until enough information is collected into the output beam scattered from the first target. The collected output beam can then be analyzed to determine various characteristics regarding the first target.
After the first target is characterized, a second target can then be moved under the incident beam so that the second target can then be characterized. Typically, multiple target characterization is realized by applying discrete movement shifts to a wafer-carrying stage so that a first target is moved in a single movement to a position under the incident beam. While the first target is characterized, the first target remains stationary. After characterization of the first target, the wafer stage is then moved again in a discrete amount so that a second target is moved to a position under the beam. While the second target is being characterized, the second target also remains stationary under the incident beam. These discrete movements require complex acceleration and deceleration mechanisms. Additionally, the time for performing these discrete wafer movements and characterization of each target can be significant.
It would be beneficial to provide improved mechanisms for performing metrology or inspection on semiconductor targets or the like.